title: Proanthocyanidins from Ginkgo biloba leaf extract and their radical scavenging activity.
abstract: BACKGROUND
  Ginkgo biloba L (Ginkgoaceae) is a traditional herbal medicinal plant for the treatment of mild to moderate cognitive disorders, tinnitus, and dementia. These uses may be correlated with the presence of radical scavenging compounds.
  
  
  OBJECTIVE
  The chemical composition and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of the flavan-3-ols and proanthocyanidins from G. biloba were studied.
  
  
  METHODS
  The compounds have been isolated using column chromatography on Sephadex LH-20 and MCI gel and the structures were determined on the basis of 1D- and 2D-NMR (HSQC, HMBC) experiments of their peracetylated derivatives, MALDI-TOF-MS and by acid-catalyzed degradation with phloroglucinol. The DPPH radical scavenging activities of the compounds were investigated.
  
  
  RESULTS
  The new trimeric prodelphinidin, epigallocatechin-(4β→8)-epigallocatechin-(4β→8)-catechin (compound 7), has been isolated from the air-dried leaves of the title plant, in addition to catechin, epigallocatechin, gallocatechin, and three dimeric proanthocyanidins. The dimeric prodelphinidin epigallocatechin-(4β→8)-epigallocatechin (compound 6) showed the strongest DPPH radical scavenging activity, with IC(50) 1.7 μg/mL, 10 times more active than the positive control, BHT (IC(50) 17.3 µg/mL), followed by the new trimeric proanthocyanidin epigallocatechin-(4β→8)-epigallocatechin-(4β→8)-catechin with IC(50) 2.1 µg/mL. The crude extract exhibited high DPPH radical scavenging activity with IC(50) 15.5 µg/mL comparable with that of BHT.
  
  
  CONCLUSIONS
  The results showed that all the isolated compounds from the tannin fraction exhibited potent free radical scavenging activities, which were higher than that of BHT, suggesting that the condensed tannins from G. biloba leaves strongly contribute to the overall antioxidant effects.
authors.affiliation: Faculty of Pharmacy, Petra University, Amman, Jordan. fqadan@gmail.com
authors.forename: Fadi
authors.initials: F
authors.lastname: Qa'dan
authors.forename: Kenza
authors.initials: K
authors.lastname: Mansoor
authors.forename: Ibraheem
authors.initials: I
authors.lastname: AL-Adham
authors.forename: Mathias
authors.initials: M
authors.lastname: Schmidt
authors.forename: Adolf
authors.initials: A
authors.lastname: Nahrstedt
mesh_terms: D016166:Free Radical Scavengers / Q000302:isolation & purification*; D020441:Ginkgo biloba / Q000737:chemistry*; D010936:Plant Extracts / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry; D044945:Proanthocyanidins / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D016166:Free Radical Scavengers; D010936:Plant Extracts; D044945:Proanthocyanidins